Electronic postage meters are well known. Such devices operate under microprocessor control to perform printing in accounting operations associated with the printing of a postal indicia on an envelope. Such accounting is usually carried out in a volatile memory and then transferred at a predetermined time to non-volatile memory for storage in the event that power is removed from the electronic postage meter.
In conventional postage meters where real-time accounting is performed, every time postage is printed, the following information is normally updated within the postage meter's memories: ascending register, descending register, piece count, batch count, and batch amount. If all this data is stored in real-time in a non-volatile memory and assumed to be stored in one buffer, this translates into the update of a 32-byte memory buffer for each accounting cycle. Normal meter lifetime specifications require 10 million accounting cycles and 1 million postage meter trips. While battery-backed CMOS RAMs used for example in U.S. Pat. No. 4,484,307 have no problem with the 100,000 WRITES per byte that such specifications call for, E.sup.2 PROMs typically have much less endurance. It will be noted there are E.sup.2 PROMs which approach this magnitude of endurance, but they are much more expensive than those with limited endurance of 10,000 WRITES per byte.
U.S. Pat. No. 4,584,647 to Eckert entitled ELECTRONIC POSTAGE METER WITH A RING COUNTER describes a ring counter in such in MNOS memory for storing a count representative of postage value. It will be appreciated that in this reference, there is no teaching of accounting for variable values of set postage. U.S. Pat. No. 4,301,507 limits the WRITE to MNOS memory simply by writing to the non-volatile memory only during a power-down sequence. In other devices, for example, a high endurance E.sup.2 PROM memory has been used for real-time accounting in non-volatile memory using the limited endurance MNOS memory only on power-down.